The equation $2^{|x^2-12|}=\sqrt{e^{|x|\log 4}}$ has
Answer & explanation
Correct answer: option 4
We have,
$2^{|x^2-12|}=\sqrt{e^{|x|\log 4}}$
$⇒2^{|x^2-12|}=\sqrt{e^{\log 4^{|x|}}}$
$⇒2^{|x^2-12|}=\sqrt{4^{|x|}}$
$⇒2^{|x^2-12|}=2^{|x|}⇒|x^2-12|=|x|$
Now, $x^2-12=0⇒ x=±2\sqrt{3}$. So, we have the following cases.
CASE I When $x ≥2\sqrt{3}$
In this case, we have
$|x^2-12|=x^2-12$ and $|x|= x$
$∴|x^2-12|=|x|$
$⇒x^2-12=x$
$⇒x^2-x-12=0$
$⇒(x-4) (x+3)=0⇒ x=4$ $[∵x≥2\sqrt{3}]$
CASE II When $x ≤-2\sqrt{3}$
In this case, we have
$|x^2-12|=x^2-12$ and $|x|= x$
$∴|x^2-12|=|x|$
$⇒x^2-12=-x$
$⇒x^2+x-12=0$
$⇒(x+4) (x-3)=0⇒ x=-4$ $[∵x≥-2\sqrt{3}]$
CASE III When $-2\sqrt{3}<x<0$
In this case, we have
$|x^2-12|=-(x^2-12)$ and $|x|= x$
$∴|x^2-12|=|x|$
$⇒-(x^2-12)=-x$
$⇒x^2-x-12=0$
$⇒(x-4) (x+3)=0⇒ x=-3$ $[∵-2\sqrt{3}<x<0]$
CASE IV When $0≤x<2\sqrt{3}$
In this case, we have
$|x^2-12|=-(x^2-12)$ and $|x|= x$
$∴|x^2-12|=|x|$
$⇒-(x^2-12)=x$
$⇒x^2+x-12=0$
$⇒(x+4) (x-3)=0⇒ x=3$ $[∵0≤x<2\sqrt{3}]$
Hence, the four real solutions are ± 4, ± 3. Clearly, their sum is zero.